IB/cma: cma_validate_port should verify the port and netdevice

Previously, cma_validate_port searched for GIDs in IB cache and then
tried to verify the found port. This could fail when there are
identical GIDs on both ports. In addition, netdevice should be taken
into account when searching the GID table.
Fixing cma_validate_port to search only the relevant port's cache
and netdevice.

Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>